The regulation of lymphocyte migration by macrophages will be studied in vitro using the random migration assay and the modified Boyden chemotaxis assay. The culture supernatants of peritoneal macrophages contain a factor(s) that is(are) chemokinetic and chemotactic for lymphocytes as observed in our laboratory. The chemokinetic activity is also present in the culture supernatants of J744A and P388D1 macrophage-like cell lines. In the proposed project the macrophage factor(s)1 will be isolated, purified and characterized, and its effect on the migration of different lymphocyte populations will be studied using lymphocyte subpopulations isolated by conventional methods and using cloned T cells. The in vivo effect of the purified factor(s) on the migration and distribution of lymphocytes will also be studied. The mechanisms of action of the factor(s) on the modulation of lymphocyte migration will be examined by studying the changes in the contractile and cytoskeletal structure of the affected cells. The proposed study is intended to gain new information on the mechanism and regulation of lymphocyte migration and localization.